Process for producing sized glass yarns



i grip 54.

- N Drawing. Filed June 4, 1957, Ser. No. 663,343

9 Claims. (CI. 28-75) This invention relates to the Warp sizing of glass fibers, and more particularly to a new and improved process for sizingglass yarns followed by coronizing of the woven fabric.

This process comprises generally the application of a polyvinyl alcohol to glass fibers, at a sufiiciently high temperature, while constantly circulating the sizing composition and weaving the fibers to form a fabric, followed by coronizing the woven fabric.

The conventional method used for the cleaning of glass fabrics, known as coronizing, comprises the passing of the fabric through a mufiie oven at a temperature of approximately 1200 F. to 1500" R, which ignites the yarn finish and leaves the glass fabric clean. This method is used in lieu of conventional de-sizing and scouring methods, which cannot produce a satisfactorily clean glass fabric. In addition to burning off all foreign matter, this treatmentsets the weave, so that the resulting fabric is softer, hangs better, and is more easily draped. Moreover, it substantially reduces fiber breakage. For these reasons, nearly all glass fabrics are coronized, eX- cept for a small percentage of fabrics which are intended for industrial uses, and therefore do not require thesuppleness of decorator fabrics.

In spite of the important advantages of the coronizing treatment, and its consequent wide-spread use, its use has presented difficult problems to the manufacturer. I Simply stated, this problem is that heretofore no one has been able to size glass fibers to be woven into fabrics which are to be coronized, and to obtain a successful commercial product.

Various methods have been attempted heretofore for the warp sizing of glass yarns, but the use of conventional sizing materials has proved unsatisfactory and unsuccessful. While these conventional materials may be satisfactory insofar as they aiford a sufficient protective coating and bond together the individual filaments, they produce readily apparent defects in the finished fabric, after cororesults in a greying. or yellowing of white glass fabrics and in a dulling of other colored fabrics, to such an extent that the final product is noticeably inferior and frequently unsaleable.

For the foregoing reasons, and even though it is high ly desirable that the warp yarns be sized in view of the chafing and rubbing together which they encounter in the loom, glass yarns are normally not sized before weavtes Patent 0 M to be objectionable.

tion, at .a temperature of F.

3,045,317 Patented July 24, 1 5

ing. This of course renders the weaving operation more difiicult.

Moreover, in order to obtain the necessary strength and break resistance in the yarn, it is necessary to use a coarser yarn, a more highly twisted yarn or a two-ply yarn, which increases the cost of manufacture.

Heretofore, in view of the above mentioned problems, it has come to be the accepted, commercial practice to size-usually with a gelatin size-the glass fibers which are to be woven into the small percentage of fabrics to be used for industrial purposes, and to use coarser, highly twisted, or two ply yarns, unsized, in the weaving of glass fabrics intended for other uses.

The process of my invention affords a practical commercial method for sizing glass yarns thereby aifording protection to the yarns and avoiding the difiiculties encountered in the weaving of unsized yarns and enabling the use of finer and cheaper yarns, yarns of lower twist, and unplied yarns, and the fabric can be coronized to produce a satisfactorily clean fabric, without the disadvantages attendant upon the use of conventional sizing materials.

This invention is applicable to any and all glass fibers or yarns, whether produced as continuous filaments or short staples, and however twisted or plied together. Typical but non-limiting examples of suitable glass yarns produced commercially are as follows:

According to the process of my invention, the yarns are sized with polyvinyl alcohol. The particular polyvinyl alcohol utilized should preferably be highly hydrolyzed and have a low ash content. I have found that the best results are obtained when using a relatively highly hydrolyzed polyvinyl alcohol, for example of the order of 86% to 1.00% hydrolysis. The more highly .hydrolized polyvinyl alcohols can be applied in smaller amounts and enable the deposit of thinner and stronger films on the yarn, and result in a superior product. Moreover, some of the polyvinyl alcohols having a higher ash content may produce a Very slight discoloration of the coronized fabric, although this will not be suflicient By way of example, we have found that Elvanol 71-30, a polyvinyl alcohol manufactured by E. I. du Pont de Nemours & Company, can be utilized to produce excellent results, as well as a number of other commercially available polyvinyl alcohols.

The polyvinyl alcohol sizing is applied in aqueous solu- I have found that it is important for this temperature to be maintained during the application of the size to the glass yarns, and that the temperature of the solution should not vary more than about 5 above or below 110 F. Generally, higher Similarly, I have found that it is desirable that the sizing bath be constantly circulated to prevent hardening, which might otherwise occur.

Following the sizing step, the yarn is Woven, and the resulting fabric is coronized in the conventional manner. The fabric thus produced is clean, free of ash, and free from burns or other defects which the use of conventional sizing processes would produce. Moreover, there is no discoloration of the fabric.

Regarding the equipment required for the process of my invention, standard slashing and coronizing equipment may be used.

The following is a typical but non-limiting example of the process of my invention.

The size formula utilized in this example consists of 31.25 pounds Elvanol 71-30 per 100 gallons of finished size. In preparing this formula, 60% cold water was drawn, the Elvanol 71-30 Was sifted in, and the resulting mixture was agitated ten minutes cold. Afterwards, the mixture was heated to 205 F. in thirty minutes, and diluted with cold water to 100 gallons. The mixture may be stored if desired, or used immediately.

A total of 2478 body ends of 150 Weight (15,000 yards weighing 1 pound) single end, untwisted Fiberglas, and 56 selvage ends of 450 weight, single end Fiberglas having a twist of 3 turns per inch are run through the slasher at the rate of yards per minute. The Quetsch pressure is 1200 pounds, and the squeeze roll is bare rubber. The cylinders are maintained at 210 F., 200 F., 200 F., 190 F., 190 -F., 180 F., 180 F., 180 F., and cold, from back to front cans respectively. The first three cans are coated with Teflon, a plastic consisting of a tetrafiuoroethylene polymer, and manufactured by E. I. du Pont de Nemours & Company. The first can is overcoated with Dow Corning Compound 20 (Silicone), manufactured by the Dow Corning Corporation. The treated yarn will be found to have a very strong but minute film of polyvinyl alcohol uniformly deposited on the surface of the yarn.

During the application of the size, the sizing bath is recirculated continuously, by overflowing into a suitable trough and being pumped back into the bath.

The cooking procedure may be varied, although the procedure described above is typical and is designed to afford maximum film strength.

Following the slashing procedure described above, the yarns are woven in conventional manner to form a fabric. The fabric thus formed is passed at the rate of approximately 825 yards per minute through a muffle oven maintained at a temperature of approximately 1400 F.

This high temperature treatment ignites the film of polyvinyl alcohol. Because of the nature of the film, and the manner in which it is applied to the yarns, the coronizing treatment results in a clean fabric, entirely free of ash, with no burns in the fabric resulting from hot spots, and without any discoloration.

As noted above, the equipment required for the process of my invention is conventional, and no special adjustments are required. However, it should be noted that the sizing composition tends to stick tenaciously to any surface with which it comes in contact, and for this reason suitable precautions, such as the coating of the first three cans, in the foregoing example, may be taken. Also, as previously discussed, the sizing composition should be constantly circulated or agitated during the passage of the glass yarns through the composition, although this precaution is not absolutely necessary in all cases.

Regarding the sizing material utilized, I have found that polyvinyl alcohol is the only satisfactory compound for producing the desired results discussed above, namely, the protection and control of glass yarns during weaving, and at the same time, enabling removal by the coronizing process without damage to the fabric and without leaving a deposit of ash. Also, during application, the temperature of the sizing bath should be maintained 4 within fairly critical limits, the preferred temperature being approximately as set forth above.

The coronizing treatment is carried out at relatively high temperatures, e.g. about 1400 F. Normally, it will not be necessary for this temperature to exceed about 1500 F., although slightly higher temperatures may be utilized, so long as the damaging point of the fabric is not reached. Generally, if temperatures in excess of l600 are utilized, an excessive softening of the fabric takes, and the warp and filling yarns may be bound together. A convenient practical minimum temperature is about 1200 F., although it is possible to use substantially lower temperatures, e.g. about 1000 F; in the latter event it is desirable, that the fabric remain in the heated atmosphere somewhat longer. Usually, the fabric passes through the oven at a rate of about 825 yards per minute, and the size and impurities flash off almost instantaneously.

The process of my invention has been described above in detail for the purpose of illustration only, and is not intended to be limited by this description or otherwise, except as defined in the appended claims.

a I claim:

1. A process of warp sizing glass yarns and cleaning glass fabrics Woven therefrom, comprising applying a size consisting of polyvinyl alcohol and water to said yarns while maintaining said size at a temperature of 105 to F. and while constantly circulating said size, drying said yarns, weaving said yarns into a fabric, and thereafter igniting said size and substantially completely burning the size off the fabric by passing the Woven fabric through an atmosphere heated to a temperature of approximately l200 to 1500 F.

2. A process for warp sizing glass yarns to bind the filaments of said yarns together and to enable control of said yarns during weaving, comprising passing said yarns through a mixture consisting of polyvinyl alcohol and water, while said mixture is maintained at a temperature of 105115 F., and drying said yarn, whereby a uniform, minute film of polyvinyl alcohol is deposited on said yarns, said film being readily ignitible and leaving no ash upon coronizing of the fabric woven from said yarns.

3. In the process of producing glass fabrics, the steps of passing glass warp yarns through a size bath consisting of polyvinyl alcohol and water maintained at a temperature of 105 -115 F., and constantly circulated to prevent hardening, and drying said yarns, whereby a uniform minute film of polyvinyl alcohol is deposited on said yarns, and igniting said film and substantially completely burning the film off said fabric by passing the fabric woven from said yarns through an atmosphere heated to a temperature of 1200-1500 F.

4. A process of producing glass fabrics comprising sizing glass warp yarns with a highly hydrolized mixture consisting of polyvinyl alcohol and water, drying said yarns, weaving said yarns into a fabric, and passing said fabric through a heated atmosphere at a temperature below the damaging point of said fabric but sufficient to ignite said polyvinyl alcohol and substantially burn said sizing off said fabric.

5. The process of producing glass fabrics of claim 4 wherein the hydrolysis of said mixture of polyvinyl alcohol and water is approximately 86%100%.

6. A process of producing glass fabrics comprising sizing warp yarns with an aqueous mixture consisting of polyvinyl alcohol and water, drying said yarns, weaving said yarns into a fabric, and passing said fabric through a heated atmosphere at a temperature below the damaging point of said fabric but sufficient to ignite said polyvinyl alcohol and substantially completely burn said sizing off said fabric.

7. A process as defined in claim 6, and in which said mixture is maintained at a temperature of l05115 F. while said mixture is being applied to said yarns.

8. A process as defined in claim 6, and in which said mixture is circulated to prevent hardening while said mixture is being applied to said yarns.

9. An improved process for producing glass fabric, comprising the steps of applying a constantly circulating size consisting of 0.3 lb. of 86%100% hydrolyzed polyvinyl alcohol per gallon of water at 105 F. to 115 F. to glass warp yarns, drying said warp yarns at a temperautre of 180 F. to 210 F. and thereby depositing a minute, uniform film of polyvinyl alcohol upon the surface of said warp yams, weaving said yarns into a fabric, and thereafter removing said size from said fabric instantaneously by igniting the size at a temperature Within the range of 1,000 to 1,600

References Cited in the file of this patent UNITED STATES PATENTS 1,920,564 Jochum et al. Aug. 1, 193 3 2,674,549 Balz Apr. 6, 1954 2,722,489 Hennessey et a1. Nov. 1, 1955 2,780,909 Bicfeld et a1. Feb. 12, 1957 2,868,669 Marzocchi et al. Jan. 13, 1959 2,879,581 Evans et al. Mar. 31, 1959 OTHER REFERENCES Du Pont Nylon Technical Service, Suggestions for Sizing," T.E.P.; D.I.B.; September 26, 1949, page 7.02. Elvenol 51-05 Polyvinyl Alcohol. 

1. A PROCESS OF WARP SIZING GLASS YARNS AND CLEANING GLASS FABRICS WOVEN THEREFROM, COMPRISING APPLYING A SIZE CONSISTING OF POLYVINYL ALCOHOL AND WATER TO SAID YARNS WHILE MAINTAINING SAID SIZE AT A TEMPERATURE OF 105* TO 115*F. AND WHILE CONSTANTLY CIRCULATING SAID SIZE, DRYING SAID YARNS, WEAVING SAID YARNS INTO A FABRIC, AND THEREAFTER IGNITING SAID SIZE AND SUBSTANTIALLY COMPLETELY BURNING THE SIZE OFF THE FABRIC BY PASSING THE WOVEN FABRIC THROUGH AN ATMOSPHERE HEATED TO A TEMPERATURE OF APPROXIMATELY 1200* TO 1500*F. 